For the right amount of money, just about anything can be converted into anything else.
I don't know the parts and clearances on your Deer Stalker.
Some manufacturers use standard clearances and parts so that it may be a matter of just inletting one of their double triggers and trigger guards from a double set gun. OR,
It may be easy to convert to a single set trigger. Single set triggers are like doubles, but it is one trigger that is pushed forward to set it. They can generally be used set or unset. There are several different heighths and shapes of trigger plates, so you should be able to find one that is a close match for your gun. A really good black powder gun smith or shop proabably has what you need. I am fortunate enough to live 80 miles from Dixon's Muzzleloader shop in PA. They have nearly every component part ever manufacturered. The problem is that you will need an experienced builder to eye things up with your rifle.